1. Field of the Invention
The present invention relates to a quantum cascade laser.
2. Related Background Art
A quantum cascade laser (QCL: Quantum Cascade Laser) is known as a semiconductor optical device. This quantum cascade laser is a promising device as a compact and low-cost light source that can be used in fields such as analysis of environmental gas, medical application, and industrial processing. As a current confinement structure of the quantum cascade laser, there is, for example, a buried heterostructure (BH: Buried Heterostructure) described in Patent Literature 1 below.
A manufacturing process of this buried heterostructure will be described. First, semiconductor epitaxial layers are grown on a semiconductor substrate, and thereafter, at least a contact layer, an upper cladding layer, and a core layer are etched to form a mesa waveguide in a region to be an optical waveguide in the center of the device. Thereafter, side walls of the mesa structure are buried by current blocking layers comprised of a high-resistance semi-insulating semiconductor to produce the current confinement structure.